Many security systems have been employed in the past to combat burglary and theft as well as fire. These systems have generally been unsatisfactory due to a high rate of false alarms and ease of defeat by intruders with knowledge of the systems weakness. For example, prior art systems utilizing key-operated locks to permit authorized personnel to enter and leave the protected premises are easily picked. Other prior art systems include capacitive, sonic, ultrasonic, and photo-electric sensing techniques; such systems, however, are sensitive to environmental conditions and are not completely reliable over a wide range of conditions of temperature and humidity, or they are subject to electrostatic and mechanical disturbances. Further, these systems make no provision for having a tenant, prior to activation of the system, automatically initiate a test of the system without notifying the appropriate responding agencies of the test.
Yet another disadvantage of security alarm systems of the prior art is the problem of ingress by individuals, say former employees, having previous access to areas surveyed by the system. One such system utilizes plastic laminated cards, issued during employment, having coded information in the form of, for instance, suitably positioned electric conducting elements of magnetic ink indicia. In this arrangement reading means is employed to "read" the information positioned on the card and if the intelligence imparted therefrom meets certain predetermined criteria, access to the surveyed area is obtained. However, such systems are expensive as is well known.